1. Field of Invention
The present invention relates to an electro-optical device having a plurality of divided cells, each of which encapsulates a dispersion system containing electrophoresis particles.
2. Description of Related Art
An electrophoresis display device using an electrophoresis phenomenon is currently known as a non-emissive display device. Herein, the electrophoresis phenomenon is a phenomenon in which when an electric field is applied to a dispersion system in which particles (electrophoresis particles) are dispersed in a liquid (dispersion medium), the particles are electrophoresed by the Coulomb force. The electrophoresis display device has a configuration in which one electrode is opposite to another electrode with a predetermined spacing therebetween, and the divided cells encapsulating the dispersion systems are arranged therebetween. Furthermore, the electrophoresis display device can include peripheral circuits for applying an electric field to the dispersion systems.
Herein, if the dispersion medium dyes with a dye and pigment is used as the electrophoresis particles, the color of the electrophoresis particles or the color of the dye is visible to an observer. In addition, a configuration of an electrophoresis display device drived by an active matrix system has been suggested (for example, see Patent Document 1). According to this configuration, first, in a reset period, a reset voltage is written to each pixel electrode. Next, in a writing period, an applied voltage is applied to each pixel electrode for a time period corresponding to a gradation value indicated by an image data. Thereafter, a common electrode voltage is applied to each pixel electrode. Thus, the charges accumulated in pixel capacitance are discharged, and then a display image is held.
In this case, when display is updated by a reset process, the spatial conditions of the electrophoresis particles are once initialized. For example, if the dispersion medium is colored in black and the electrophoresis particles are white, the whole screen is blacked out. Since humans cannot perceive variations for a short time, a moving picture may be displayed taking no thought of the reset process if a time period required for the reset process is short. However, a long time period may be required for the reset process in accordance with physical features of the dispersion system, and thus the variations in density due to initialization of the electrophoresis particles may be perceived.
Therefore, in order to solve such a problem Japanese Unexamined Patent Application Publication No. 2002-116734 discloses a configuration in which a voltage corresponding to the difference between the mean position of the electrophoresis particles corresponding to a gray scale to be displayed next and the mean position of the electrophoresis particles corresponding to a gray scale currently being displayed is applied between both electrodes for a fixed period of time. By this configuration, it is possible to update the display without the reset process, and thus it is possible to efficiently display a moving picture.
However, in the electrophoresis display device using the differential voltage, when drift is generated in the positions of the electrophoresis particles, the drift also appears in the next display. In this case, it is impossible to execute an accurate display. Furthermore, the drift may be superposed and promoted. In addition, it is possible to correct the drift by periodically carrying out the reset process. However, when the whole electrophoresis display panel is simultaneously reset, the variation in the display density in carrying out the reset process may be perceived.
The present invention is provided to solve the above problems, and it is an object of the present invention to provide an electro-optical device, a method of driving the electro-optical device, and an electronic apparatus, capable of maintaining much higher display quality.
An electro-optical device according to the present invention can include a plurality of pixels and a control device that controls the display density of the plurality of pixels. The control device for carrying out a display process based on first data and then carrying out a display process based on second data can select first pixels and second pixels from the plurality of pixels. With respect to the first pixels, the control device calculates a differential data between the first data and the second data, and then carries out a first display process based on the differential data. With respect to the second pixels, the control device carries out a reset process on the pixels, and then carries out a second display process based on the second data.
According to this configuration, as for the first pixels, since the display process is carried out based on the differential data between the image data previously displayed and the image data to be displayed next, it is possible to omit the reset process, and thus to efficiently carry out the image display. Furthermore, as for the second pixels, the display process is carried out after the reset process of the pixels. Therefore, it is possible to correct the drift generated due to the display process based on the differential data. In this case, since the second display process is carried out on a part of the pixels, it is possible to suppress the variation in display density due to the reset process.
In this electro-optical device, the second pixels are selected as dispersed ones from the plurality of pixels.
Thus, since the spatially separated reset process can be carried out, it is possible to suppress the variation in display density due to the reset process.
According to this electro-optical device, the plurality of pixels can include a common electrode, pixel electrodes opposite to the common electrode, switching elements connected to each of the pixel electrodes, and dispersion systems containing electrophoresis particles between the common electrode and the pixel electrodes, and the display process is carried out by moving the electrophoresis particles using a voltage applied between the common electrode and the pixel electrodes, and a applying time of the voltage.
According to this configuration, the electro-optical device employing the electrophoresis elements can carry out the first and second display processes. Therefore, by carrying out the reset process on a part of the pixels while correcting the drift generated due to the display process based on the differential data, it is possible to suppress the variation in display density due to the reset process.
In this electro-optical device, all the second pixels are selected within a predetermined period of time. By doing so, the reset processes on all the pixels can be carried out within a predetermined period of time.
In this electro-optical device, the display density has two or more polarities, and the reset process on the second pixels includes reset processes different in polarity. By doing so, the display density in carrying out the reset process is counterpoised. When the reset process of one polarity is carried out, a deflection of the display density may be generated in carrying out the reset process. By including reset processes different in polarity, it is possible to counterpoise the variation in the display density due to the reset process.
In this electro-optical device, the reset processes different in polarity are carried out on the second pixels adjacent to each other. By doing so, it is possible to further counterpoise the variation in the display density due to the reset process.
In this electro-optical device, when the second data includes a data for displaying the display density having a predetermined value or more, the second display process is carried out on the second pixels. Thus, it is possible to efficiently perform the second display process on the pixels, with which the display close to the reset condition is carried out.
In this electro-optical device, the reset process carried out on the second pixel comprises a former frame period for performing only the reset process on the pixels and a latter frame period for performing the second display process based on the second data. According to this configuration, since it is not necessary to continuously write the reset and the display data to the same pixel, a temporal margin is generated. Thus, it is possible to simplify a circuit construction.
A method of driving an electro-optical device according to the present invention is a method of driving an electro-optical device including a plurality of pixels and a control device that controls display density of the plurality of pixels. The control device can perform the step of carrying out a display process based on first data. When a display process is carried out based on second data, the device can select first pixels and second pixels from the plurality of pixels. With respect to the first pixels, the device can calculate a differential data between the first data and the second data and then carrying out a first display process based on the differential data. With respect to the second pixels, the device can carry out a reset process on the second pixels and then carrying out a second display process based on the second data.
According to this configuration, as for the first pixels, since the display process is carried out based on the differential data between the image data previously displayed and the image data to be displayed next, it is possible to omit the reset process and thus to efficiently perform the image display. Furthermore, as for the second pixels, the reset process is carried out on the pixels, and then the display process is carried out. Therefore, it is possible to correct the drift generated due to the process using the differential data. In this case, since the second display process is carried out on a part of the pixels, it is possible to suppress the variation in display density due to the reset process.
In this method of driving the electro-optical device, the reset process on the second pixels can include a former frame period for carrying out only the reset process on the pixels and a latter frame period for carrying out the second display process based on the second data. According to this configuration, since it is not necessary to continuously write the reset and the display data to the same pixel, a temporal margin is generated. Thus, it is possible to simplify the circuit construction.
An electronic apparatus according to the present invention can also be equipped with the electro-optical device described above. According to this configuration, the electronic apparatus can have low power consumption and a high display quality simultaneously.